Which of the following is classified as a day signal?

An orange smoke signal is classified as a day signal because it produces a highly visible plume of smoke that can be seen from a distance during daylight hours. This type of signal is specifically designed for use in bright conditions and is effective in alerting nearby boaters and rescuers of distress or the need for assistance. The bright orange color of the smoke stands out against the natural backdrop, making it a highly recognizable signal during the day.

Other options like a red flare are intended for use at night, as they produce a vivid light that is more effective when the surroundings are dark. A handheld VDS (Visual Distress Signal) is also typically used in various conditions but the effectiveness of such devices often varies based on the environment and visibility. A whistle, while useful for communication and signaling in certain situations, does not produce a visual signal and is not classified as a daytime visual distress signal. Thus, the orange smoke signal is the most suitable choice for a daytime signaling device.